This invention relates to optical devices, and more particularly to optical waveguide devices.
In the integrated circuit industry, there is a continuing effort to increase device speed and increase device densities. Optical systems are a technology that promise to increase the speed and current density of the circuits. Optical devices, such as optical interconnectors, modulators, deflectors, and lenses are components in these optical systems. Such optical devices can be used to perform a variety of functions in integrated circuits such as switching or data transmission. Optical devices that perform different functions are typically formed and shaped differently in order to perform the different functions. As such, each type of optical device, and each size of the same optical device type, has to be manufactured distinctly. Therefore, the production of precision optical devices is expensive.
Additionally, passive optical waveguide devices are susceptible to changes in temperature, contact, pressure, humidity, etc. As such, the optical devices are typically contained in packaging that maintains the conditions under which the optical devices are operating. Providing such packaging is extremely expensive. Even if such packaging is provided, passive optical devices may be exposed to slight condition changes. As such, the passive optical devices perform differently under the different conditions. For example, the modulators will modulate the light a different amount and the optical deflectors will deflect the light to a different angle, etc. If the characteristics of a passive optical device is changed outside of very close tolerances, then the optical device will not adequately perform its function. In other words, there is no adjustability to the passive optical devices.
It would therefore be desirable to provide an optical device that can be produced using more uniform components while providing a wide range of functionality. Additionally, it would be desired to provide an active optical device whose operation can be adjusted by slight modification to the structure of the device.
The present invention is directed to an apparatus and associated method for changing the effective mode index or the propagation constant in a region of changeable propagation constant in a waveguide. The method comprises changing the free-carrier distribution in the semiconductor waveguide. This is accomplished by using the same semiconductor waveguide as part of a Field Effect Transistor (FET) of Metal Oxide Silicon capacitor (MOSCAP) with at least one electrode in contact with the semiconductor and the other electrode of a prescribed electrode shape proximate to the waveguide separated by an electrical insulator. Application of the voltage between the electrodes leads to a changeable propagation constant and an changed effective mode index in a region of changeable propagation constant in the waveguide due to the changes in the free-carrier distribution. This change in local level of effective mode index propagation constant in a region of changeable propagation constant roughly corresponds, in shape, to the shaped electrode. Thus, the effective mode index or the propagation constant in the region of changeable propagation constant in the waveguide is controlled by application of the voltage to the shaped electrode.
The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiment of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention.
FIG. 1 shows a front cross sectional view of one embodiment of an optical waveguide device including a field effect transistor (FET);
FIG. 2 shows a top view of the optical waveguide device shown in FIG. 1;
FIG. 3 shows a section view as taken through sectional lines 3xe2x80x943 of FIG. 2;
FIG. 4 shows a front cross sectional view of one embodiment of an optical waveguide device including a metal oxide semiconductor capacitor (MOSCAP);
FIG. 5 shows a front view of another embodiment of an optical waveguide device including a high electron mobility transistor (HEMT);
FIG. 6 shows a graph plotting surface charge density and the phase shift, both as a function of the surface potential;
FIG. 7 shows one embodiment of a method to compensate for variations in temperature, or other such parameters, in an optical waveguide device;
FIG. 8 shows another embodiment of a method to compensate for variations in temperature, or other such parameters, in an optical waveguide device;
FIG. 9 shows a top view of another embodiment of optical waveguide device 100;
FIG. 10 shows a side cross sectional view of one embodiment of a ridge optical channel waveguide device;
FIG. 11 shows a side cross sectional view of one embodiment of a trench optical channel waveguide device;
FIG. 12 shows one embodiment of a wave passing though a dielectric slab waveguide;
FIG. 13 shows a top view of another embodiment of an optical waveguide device from that shown in FIG. 2, including one embodiment of a prism-shaped gate array that provides for light deflection by the optical device;
FIG. 14 shows a top cross sectional view of the waveguide of the embodiment of prism-shaped gate array of FIG. 13 including dotted lines representing a region of changeable propagation constant. The solid light rays are shown passing through the regions of changeable propagation constant corresponding to the prism-shaped gate array;
FIG. 15, including FIGS. 15A, 15B, 15C and 15D, show side cross section views of the optical waveguide device of FIG. 13 or taken through sectional lines 15xe2x80x9415 in FIG. 13, FIG. 15A shows both gate electrodes 1304, 1306 being deactivated, FIG. 15B shows the gate electrode 1304 being actuated as the gate electrode 1306 is deactivated, FIG. 15C shows the gate electrode 1304 being deactuated as the gate electrode 1306 is activated, and FIG. 15D shows both gate electrodes 1304 and 1306 being actuated;
FIG. 16 shows a top view of another embodiment of an optical waveguide device that is similar in structure to the optical waveguide device shown in FIG. 2, with a second voltage source applied from the source electrode to the drain electrode, the gate electrode and electrical insulator is shown partially broken away to indicate the route of an optical wave passing through the waveguide that is deflected from its original path along a variety of paths by application of voltage between the source electrode and gate electrode;
FIG. 17 shows another embodiment of an optical deflector;
FIG. 18 shows a top view of one embodiment of an optical switch that includes a plurality of the optical deflectors of the embodiments shown in FIGS. 14, 15, or 16;
FIG. 19 shows a top view of another embodiment of an optical switch device from that shown in FIG. 18, that may include one embodiment of the optical deflectors shown in FIGS. 14, 15, or 16;
FIG. 20 shows one embodiment of a Bragg grating formed in one of the optical waveguide devices shown in FIGS. 1-3 and 5;
FIG. 21 shows another embodiment of a Bragg grating formed in one of the optical waveguide devices shown in FIGS. 1-3 and 5;
FIG. 22 shows yet another embodiment of a Bragg grating formed in one of the optical waveguide devices shown in FIGS. 1-3 and 5;
FIG. 23 shows one embodiment of a waveguide having a Bragg grating of the type shown in FIGS. 20 to 22 showing a light ray passing through the optical waveguide device, and the passage of reflected light refracting off the Bragg grating;
FIG. 24 shows an optical waveguide device including a plurality of Bragg gratings of the type shown in FIGS. 20 to 22, where the Bragg gratings are arranged in series;
FIG. 25, which is shown exploded in FIG. 25B, shows a respective top view and top exploded view of another embodiment of an optical waveguide device including a gate electrode configured that may be configured as an Echelle diffraction grating or an Echelle lens grating;
FIG. 26 shows a top cross sectional view taken within the waveguide of the optical waveguide device illustrating the diffraction of optical paths as light passes through the actuated Echelle diffraction grating shown in FIG. 25, wherein the projected outline of the region of changeable propagation constant from the Echelle diffraction grating is shown;
FIG. 27 shows an expanded view of the optical waveguide device biased to operate as an Echelle diffraction grating as shown in FIG. 26;
FIG. 28 shows a top cross sectional view taken through the waveguide of the optical waveguide device illustrating the focusing of multiple optical paths as light passes through the actuated Echelle lens grating shown in FIG. 25, illustrating the region of changeable propagation constant resulting from the Echelle lens grating;
FIG. 29 shows an expanded view of the optical waveguide device biased to operate as an Echelle lens grating as shown in FIG. 28;
FIG. 30 shows a top view of one embodiment of an optical waveguide device that includes a Bragg grating, and is configured to act as an optical lens;
FIG. 30A shows a top cross sectional view taken through the waveguide of the optical waveguide device shown in FIG. 30 illustrating light passing through the waveguide;
FIG. 31 shows a top view of another embodiment of optical waveguide device that includes a filter grating, and is configured to act as an optical lens;
FIG. 31A shows a top cross sectional view taken through the waveguide of the optical waveguide device shown in FIG. 31 illustrating light passing through the waveguide;
FIG. 32 shows a top view of another embodiment of optical waveguide device that includes a Bragg grating, and is configured to act as an optical lens;
FIG. 32A shows a top cross sectional view taken through the waveguide of the optical waveguide device shown in FIG. 32;
FIG. 33 shows a front view of another embodiment of optical waveguide device from that shown in FIG. 1;
FIG. 34 shows a top view of one embodiment of an arrayed waveguide (AWG) including a plurality of optical waveguide devices;
FIG. 35 shows a schematic timing diagram of one embodiment of a finite-impulse-response (FIR) filter;
FIG. 36 shows a top view of one embodiment of an FIR filter;
FIG. 37 shows a schematic timing diagram of one embodiment of an infinite-impulse-response (IIR) filter;
FIG. 38 shows a top view of one embodiment of an IIR filter;
FIG. 39 shows a top view of one embodiment of a dynamic gain equalizer including,a plurality of optical waveguide devices;
FIG. 40 shows a top view of another embodiment of a dynamic gain equalizer including a plurality of optical waveguide devices;
FIG. 41 shows a top view of one embodiment of a variable optical attenuator (VOA);
FIG. 42 shows a top view of one embodiment of optical waveguide device 100 including a channel waveguide being configured as a programmable delay generator 4200;
FIG. 43 shows a side cross sectional view of the FIG. 42 embodiment of programmable delay generator 4200;
FIG. 44 shows a top view of one embodiment of an optical resonator that includes a plurality of optical waveguide devices that act as optical mirrors;
FIG. 45 shows a top cross sectional view taken through the waveguide of the optical resonator shown in FIG. 44;
FIG. 46 shows a top view of one embodiment of an optical waveguide device configured as a beamsplitter;
FIG. 47 shows a top view of one embodiment of a self aligning modulator including a plurality of optical waveguide devices;
FIG. 48 shows a top view of one embodiment of a polarizing controller including one or more programmable delay generators of the type shown in FIGS. 42 and 43;
FIG. 49 shows a top view of one embodiment of an interferometer including one or more programmable delay generators of the type shown in FIGS. 42 and 43; and
FIG. 50 shows a flow chart of method performed by the polarization controller shown in FIG. 48.